In one conventional form of V-belt structure the V-belt is defined by a body of rubber having a trapezoidal cross-section. A plurality of low elongation, high strength tensile cords are provided in parallel transversely spaced relationship to extend longitudinally through the body intermediate the upper and lower faces of the body. The lower portion of the body defines a compression section and the upper portion of the body defines a tension section.
It is further conventional to provide such V-belts with reinforcing fabric on one or both of the upper and lower faces. Such fabrics may be provided in one or more layers on the respective faces.
In one conventional form of such a V-belt known as a raw edge-type V-belt, the side faces of the V-belt are uncovered.
As the belt body is formed of a flexible rubber material, the belt provides desirable bending strength.
However, when the belt is entrained about a pulley in the drive system, lateral pressure causes the belt to expand laterally against the pulley surfaces tending to increase friction and noise. In an effort to stiffen the belt against this lateral expansion, it has been common to provide in the belt short staple fibers such as Stiflex fibers which are arranged to extend in the transverse direction to provide enhanced lateral stability and resistance to expansion.
However, it has been found that the use of such Stiflex material has not provided sufficient resistance to transverse expansion, particularly where the belt is used in high power transmission systems. Illustratively, such belts have been found to be unsatisfactory for use as power transmission belts in torque converters such as used in motorcycles, farm appliances, etc.